1. Field of the Invention
The present invention relates to flame resistant starch-sulfamate products, a process for manufacturing them and their uses.
2. The Prior Art
It is well known that starches and modified starches are useful alone or in combination with synthetic polymers as comparatively inexpensive fillers, thickeners and binders. They are also used to make adhesives for wet-end and surface sizing in paper-making and paper-processing and corrugating as well as for coating and bonding paper and board, in the manufacture of composite materials and as binders in paints, adhesives, fillers, putty and coating compositions.
Known starch products have various deficiencies such as high flammability, insufficient viscosity stability, lack of water-resistance, incompatibility with synthetic polymers, lack of thermoplastic properties and, consequently, lack of heat-sealability.
There have been attempts to remedy these shortcomings. They have only been moderately successful, especially with regard to flammability and thermoplastic properties. Improvements achieved were limited, required a considerable amount of effort or were effective only in respect of one or a few desired functional properties.
The improvement in flame-resistance of starches was done in the prior art by blending and, optionally, reacting the starch with phosphates. This gave starch products which were sufficiently flame-resistant themselves, but generally were not suitable for imparting adequate flame-resistance to the materials treated with them such as papers, boards, or textiles sized, coated or finished with them or plastic materials blended with them. With respect to other properties requiring improvement, specifically heat-sealability, these products failed to give satisfactory results.
It is the object of this invention, therefore, to overcome the disadvantages of the prior art and, specifically, to provide new low-cost starch products having high flame-resistance and other desired properties such as high viscosity stability, water resistance, high bonding strength on substrates such as paper, plasterboard, glass and mineral fibers, metal and plastic materials, rigid foams, mineral boards and stone, and having thermoplastic properties, giving flexible, water-repellent, clearly transparent and heat-sealable, flame-resistant films.
The object is accomplished by reacting gelatinized starches with sulfamates. Sulfamates are commonly known flame-retardant agents which are used, for example, for making textiles and papers flame-resistant (see U.S. Pat. Nos. 2,142,116, 2,212,152 and 2,452,054 and German DE-PS No. 904 524). However, they have not previously been reacted with gelatinized starches to give products having the characteristics disclosed in the present specification.